In a conventional liquid crystal display using an active matrix type liquid crystal panel, alternating current drive is applied to liquid crystal elements by inverting the polarity of the data signals to prevent the liquid crystal elements from being degraded.
FIG. 1 is a schematic diagram of a conventional, liquid crystal display as described above. In the figure, a gate driver 1 is connected to n row conductors G1 to Gn to which scanning signals are sequentially applied. A first data driver 2 is connected to odd column conductors D1 to Dm-1 to which first data signals are applied. A second data driver 3 is connected to even column conductors D2 to Dm to which second data signals are applied. TFT's 4a, 4 b, 4c, and 4d are provided at the respective intersections of the row conductors and the column conductors, with each one of their gate electrodes being connected to a corresponding one of the row conductors, each one of their drain electrodes being connected to a corresponding one of the data signal lines, and their respective source electrodes being connected to subpixels 5a, 5b, 5c, and 5d as described below. Subpixels 5a, 5b, 5c, and 5d, each of which is a liquid crystal cell, are driven by the TFT's 4a, 4b, 4c, and 4d, respectively.
For area gradation of these subpixels (i.e. to display grey scale) a single pixel is comprised of the four adjacent subpixels 5a, 5b, 5c, and 5d which may also be vertically or horizontally arranged. In this case, predetermined levels of gradation over a range of grey scale can be displayed by selecting properly the ratio of the sizes or areas of the subpixels 5a, 5b, 5c, and 5d.
The conventional method for driving the subpixels of FIG. 1 is as follows. First, gate signals are sequentially applied to the gate electrodes of the TFT's 4a, 4b and 4c, 4d (connected to their respective row conductors), by the gate driver 1 in response to control signals from a controller (not shown). TFT's 4a, 4b and 4c, 4d are sequentially turned on. A first data signal and a second data signal are applied to each column conductor simultaneously with these gate signals, from the first data driver 2 and the second data driver 3. The first and the second data signals may have the same polarity or opposite polarity and, are inverted every frame.
When the first and the second data signals are signals of the same polarity, the polarity of signal applied to all subpixels on the entire display screen is simultaneously inverted every frame.
However, when the first and the second data signals are signals of opposite polarity, subpixels on the entire display screen are inverted and driven by signals of opposite polarity in the row direction.
In the conventional liquid crystal display as described above, data signals having the same phase are inverted every frame and are applied to each odd data signal line and each even data signal line respectively. Noticeable flicker is present because the entire display screen is driven by alternating current which is inverted in polarity every frame.
It will be appreciated that when data signals having opposite phase, which are inverted every frame, are applied to each odd data signal line and each even data signal line, respectively, noticeable flicker on the screen is present to almost the same degree as in the case where data signals with the same phase are applied, as described above. This is because the entire display screen is driven by alternating current which is changed in polarity every sub pixel in the row direction.